Enable download home by default

chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java

Index: chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java b/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java
index d47702ee6c9a696b22dca550994f7d76c69fb468..eb3327efb05eb3dc0b5815f3ed7d5abec4952e4a 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java
@@ -80,6 +80,8 @@ public class DownloadManagerService extends BroadcastReceiver implements
     // Wait 10 seconds to resume all downloads, so that we won't impact tab loading.
     private static final long RESUME_DELAY_MILLIS = 10000;
     private static final int UNKNOWN_DOWNLOAD_STATUS = -1;
+    private static final String PREF_IS_DOWNLOAD_HOME_ENABLED =
+            "org.chromium.chrome.browser.download.IS_DOWNLOAD_HOME_ENABLED";
 
     // Values for the histogram MobileDownloadResumptionCount.
     private static final int UMA_DOWNLOAD_RESUMPTION_MANUAL_PAUSE = 0;
@@ -242,6 +244,8 @@ public class DownloadManagerService extends BroadcastReceiver implements
             long updateDelayInMillis) {
         mContext = context;
         mSharedPrefs = ContextUtils.getAppSharedPreferences();
+        // Clean up unused shared prefs. TODO(qinmin): remove this after M58.

[Theresa, 2017/01/25 22:56:49]

nit: What if the user is updating from M56 to M59 (or M65)?

[qinmin, 2017/01/26 00:18:12]

Unfortunately, that will leave the sharedpref uncleaned. Hopefully, a majority
of the user will either upgrade to M57 or M58, and thus they won't have such
issue.

[Theresa, 2017/01/26 00:22:21]

Why not just leave this line until a more distant milestone?

[qinmin, 2017/01/26 00:39:53]

ok, changed this to M61, that is 30 weeks since M56, more than half a year since
the flag is gone.

+        mSharedPrefs.edit().remove(PREF_IS_DOWNLOAD_HOME_ENABLED).apply();
         mDownloadNotifier = downloadNotifier;
         mUpdateDelayInMillis = updateDelayInMillis;
         mHandler = handler;